Abstract
A new carbonization process with rapid preheating and coke discharging at medium temperature has been developed in Japan. The result of this process shows that even when non or slightly coking coal is by 50wt% the coking property is improved and a coking coke with cold strength usable at blast furnace can be manufactured with the new carbonization process. The mechanism for the improvement of the coking property was examined by coal properties with using mainly in-situ NMR imaging. To monitor the dynamical changes in coals with temperature, an in-situ method must be used, therefore, we have applied Single-Point-Imaging and have carried out the first systematic in-situ variable-temperature NMR imaging study of coals between 25 and 500°C with our newly developed high temperature imaging probe and systems. It has been clarified that the macromolecular structure of coal is relaxed by the rapid heat treatment and in addition there is a close relation in hydrogen bond and relaxation of molecular structure of coal. The fact that rapid heating treatment of coal raised on DI150 is at almost 6 point in the treatment of temperature at 380°C, compared to the raw sample and slow heat sample is mainly caused by the decreasing of unsoftened area in coal. Rapid heat treatment is that the cohesion structure of coal molecule is relaxed by rapid heat and the kinetic property of molecule increases. And further, a bridge forming reaction generated by slow heating is suppressed and high mobility component increases and as the above results, a softening and melting phenomenon is accelerated as a time of coking. Finally, we would like to propose the mechanism for the improvement of the coking property during this rapid heat treatment, which have the improvement of coal properties.
